Fuse construction



:v/u ma 4me :MM M/ 7 e mw M t .5 2 iff 4 F M m\\ m C w mm K Hw, 0W am DMW Aug. 8, 195o Flled Jan 6, 1947 Aug. 8, 1950 c. H. BAKER FUSE CONSTRUCTION 4 Sheets-Sheet 3 Filed Jan. 6, 1947 Aug. 8, 1950 C, H, BAKER 2,517,624

FUSE CONSTRUCTION Filed Jan. 6, 1947 4 Sheets-Sheet 4 6A #i 29 h?. 6,5

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Patented Aug. 8, 1950 FUSE `CONSTRUCTION Charles H. Baker, Maywood, Ill.,

assignor to S '& lC Electric Company, a corporation of Delaware Application January 6, 1947, Serial No. 720,428

(ICI. 200-120) 23 Claims. l

This invention relates, generally, to circuit interrupting devices, and it has particular relation to fuses for use on alternating-current electricpower systems operating at high voltages, of the order of 115 kv., where the transient recovery voltage may be substantially greater than the normal-frequency recovery-voltage, and where both large and small fault-currents may be encountered.

The present invention relates to the fuse construction disclosed in the copending application of Sigurd I. Lindell and Charles H. Baker, Serial No. 663,832, led April 22, 1946. It may be ernployed with the terminal construction as shown in the copending application of Sigurd I. Lindell, Serial No. 663,833, led April 22, 1946, now Patent No. 2,484,839, issued October 18, 1949, and in the dropout fuse construction disclosed in the copending application of Sigurd I. Lindell, Serial No. 663,834, led April 22, 1946.

Fuses are extensively used in the primary connections to high voltage transformers, and must be capable of clearing any fault current within the wide range of values obtainable in such service. For example, a shortcircuit at the primary terminals will draw the full short-circuit current that the generators and transmission equipment can deliver to that point, which on a typical 115 kv. circuit may be as high as 6000 amperes. A fault in the secondary circuit must draw its power through the impedance of the transformer and so will produce a much lower primary current but of low power factor. An extreme case is presented by a potential transformer. Such a transformer sup-plying only meters and relays may draw a primary current of a few milliamperes under normal operation, and only a few amperes even when the secondary (output) terminals are short-circuited. In other installations, faults may be encountered that give rise to primary currents between these extreme values. A fuse must be capable of promptly and surely interrupting any value of current from the lowest that will sever its fusible element to the maximum that the system can deliver to it on a short circuit. v

In a fuse of this type the arc-passageway must be large enough to handle the largest possible fault currents without producing destructive pressures, but a small current, which the fuse must be also capable of interrupting, produces an arc or small cross section which tends to be blown away from the walls of the passageway and does not excite the production of sufcient arc-extinguishing gas (such as water vapor) from those Walls for the effective extinction of the arc.

In accordance with the present invention a sealed reservoir is provided which contains a fluid, such as carbon dioxide, that, when released into the arc-passageway, quickly lls it and provides a blast action in the arc-passageway which tends to sweep out the products of the arc and to scavenge the inner surface of the arc-passageway to remove therefrom material likely to form a conducting path thereover.

In some fuse constructions, it may be desirable to release the fluid from the reservoir immediately upon the occurrence of a fault and before the terminal in the arc-passageway begins to move therethrough to extend the arc. In other instances, it may be desirable to delay the introduction of the fluid from the reservoir until the terminal has completed its movement through the arc-passageway.

In accordance with the present invention, provision is made for initiating the functioning of the fuse in response to low currents, such as those produced in the primary circuit of a potential transformer on the occurrence of a secondary fau-lt. This, in combination with the provision of the reservoir containing the arc-extinguishing fluid which is released into the arc-passageway, provides a construction which will quickly and reliably interrupt the ilovv of fault current before any damage can be done to the transformer and without harm to adjacent equipment, as might be the case if the arc, once drawn by the fuse, were not promptly extinguished.

However, the present invention is not limited solely for use with fuses of low current ratings, such as those used for potential transformers. Provision is made for carrying the current carrying capacity of the fuse up to higher values by employing, in addition to a strain element, a fusible element having relatively large current carrying capacity.

Accordingly these are among the objects of this invention: To provide a low current high-voltage fuse which shall be simple, eflicient and accurate in operation; to release an arc-extinguishing fluid from a container or reservoir to flow into the arc-passageway of the fuse immediately upon the melting of the fusible element and before lengthening the arc; to cause the arc-extinguishing fluid to flow through a tubular terminal, movable through the arc-passageway which constitutes one of the terminals between which the arc incident to circuit interruption is drawn; to restrain the operating mechanism of lthe fuse by a strain wire that extends through a tubular of a fuse mounting (not shown) as is more fully set forth in the copending application of Sigurd I. Lindell, Serial No, 663,833, referred to hereinbefore. The terminals I`I and I2 are formed of suitable conducting material, such as brass.

As disclosed more fully in the copending application of Sigurd I. Lindell, Serial No. 663,834, alsoreferred to hereinbefore, the fuse'v herein disclosed is arranged to be mounted so that, when the fuse blows, it will automatically move or swing in its fuse mounting, under the influence attached to the terminal remains stationary; vand f to increase the current rating of the fuse construction by employing a fusibleel'ement-in addition to the strain element which serves to re'- strain the operating mechanism until the fuse blows.

Other objects of this invention will be obvious and in part`-appear hereinafter.

This invention is disclosed in the embodiments thereoff shown Ain theA accompanying. drawings and it comprises theffeatures of construction, combination of elements and arrangement of parts which-will beexempliiied in theV constructions hereinafter set forth and thescope of the application oflwhich will be=indicated-in the appended claims. -Fora more lcomplete understanding of the nature and-scope of this invention reference can be had to the following detailed description taken in connection lwith the accompanying drawings, inf-which:

Figures lA-lB-lC, taken together,-show alongitudinal, sectional `View through -a fuse construction in rwhich the present invention is embodied,- the-fusebeingj shown in theunblown condition, Figure 1B being broken near the -midsection'inr` order to showY the details-of-construction at the scale chosen within'the limits of the space available; v Y Figure 2v isa detailedsectional view; at a larger scale, of the-fuse construction -as shown in the preceding `figures at the sectionadjacent-the reservoir, showing the relative positions of the various parts immediately after thecurrent responsiveelement has parted'and the lost motion liasfbeen taken up for puncturingthe gas-containing reservoir, and before the terminal in the arc-passageway has begun to move;

' IFigure 3 isa detailed sectional view taken along the-line 3--3 of Figure 2;

Figure 4 is a detailed sectional view taken along the line lI-4 of Figure 2;

' Figures 5A-5B, taken'- together, constitute a viewsimilar to Figures lA-lB, showing the relativef positions of the various parts of the fuse in'ful-ly-operated condition after -bei-ng blown by a short circuit;

f Figures A-Billustrate a modiiication of' the fuse construction shown in Figures lA-lB-l'C having a solid rather than a hollow-needle for puncturing the diaphragm, having a current-responsive element of a type used for higher loadcurrents; and

Figure 7 is a detailed sectional view takenalong the line "I-'T of Figure 6B.

Referring now particularly to` Figures 1A, 1B and lC-of the drawings, it will be observed that the reference character It designates an insulating tube which forms the housing -cf the fuse or circuit interrupter to be ydescribed in detail hereinafter. At its oppositeends theinsulating tube I0 is provided with external or line vterminals II and -I2 whicharearranged tohave contact engagement lwith suitable terminal clips in part oflgravity and the biasing force of the contact clips, to a position in which an air gap is provided betweenlthel-upperline terminal II and the associ'atedk terminal clip which is connected to the circuit. In order to provide such operation the v*fusehas alatch` tube I3 which is secured at its lower end to a latch release iiange I4 that, to-

= gether with the tube I3, is arranged to be moved upwardly in a manner to be described hereinafter for the purpose ofunlatching the locking mechanism on the fuse mounting and permitting theufuse to fall, or drop out, .to the open-.circuit position.

. The fuse is arranged to; expel the gases from the arc l*downY vthrough thel lower line terminal I2'. In order Ytoicooland condense the arc products 'and limit the escape of fiarne fromthe lower end of the fuse, a condenser assemblyv may be provided on the'lower line terminal I2: Its shell is indicated at I6. The internal details-of-constructionof the condenser will be set forthmore fully hereinafter.

Particular reference willnow be made to` Figure 1B. As there shown-the fuse tube I0 is formed ofinsulating material. This may be a phenolic condensation product, such as Bakelite or it may be melamine. The tube III may be formed of a-solid,` rolled, phenolic-condensation-product and may-'have a bakedcoating of melamine-enamel on the outside land the inside to provide -weather and arc-resisting surfaces superior in these respectsto the surface of the tube itself.

At the central portion of the tube I 0 its internaldiameter-is smaller as indicated at I8 for the purpose of providing a section which has greater resistance to bursting pressure, Vbecause high pressures may be generated within the -tube IB in theportion thereof inwhich thel arc is drawn andextinguished. This configuration also aids in more uniformly distributing the dielectric flux-in the air outside of the tube I0 about the'ends'of the terminals embedded in the tube.

With al view to providing an arcing passageway from whose surface an arc-extingushing medium can be evolved, cakes `I9 of solid, arc-extinguishing material are positioned'along the bore of the small diameter section I 8. 1 These cakes I il are annular in form and when placed one" above the other/provide a continuous bore 20'in which-the arc may be drawnancl` extinguished; VVarious solid, arc-extinguishing materials may bel employed. For example, boric acid or. magnesium borate'may be used.

As indicated in the copending application of Lindell and'Baker, Serial No. 663,832, referred to hereinbefore; diiiiculty has been` encountered in the failure of the fuse as a result of arcingover along the juxtaposed surfacesof the tube I0J and the solid arc-extinguishing material I9. This diiiicultyhas been overcome, as there disclosed, by grooving the thickened portion VI8 of the wall of theA tube IIJ, by *threadingv` the same as Vindicated 'at 2|.' "Thelfcakes I9 of 'solid'arc-extingu-ishing material, such as boric acid or magnesium borate, are placed inthe fuse tube l0 and then are successively subjected to a molding pressure `so that they are compacted, one by one, into intimate engagement with the melamine coated threads 2l, leaving the central bore 29 which forms the arc-passageway.

l At each end of the column of cakes I9 of solid arc-extinguishing material there is provided a reenforcing ring of suitable insulating material, such as liber. One of these is indicated at 24 at the upper end in Figure 1B and the other is indicated at 25 at the lower end. The reenforcing ring 25 is liared outwardly to facilitate the outward iiow of the products of the arc, as will be readily understood.

Movably mounted within the bore 29 in the cakes I9 of solid, arc-extinguishing material is a hollow, rodlike or tubular terminal 26. The terminal 26 is movable through the bore 20 by mechanism which will be described in detail hereinafter. At its upper end the terminal 26 is provided with a contact tip 21 which, as shown, is threaded onto it. As shown more clearly in Figure 2 the contact tip 21 has a circumferential groove .28 for receiving thevinturned ends of contact iingers 29 that are biased inwardly by a garter spring 3D. The contact fingers 29 are formed by longitudinally slotting a tubular shell 3|. The base section of the shell 3| may be rolled into a flange 32 which extends upwardly from a contact iitting 33, the lower end of which is shaped to conform to the adjacent surface of the fuse tube lll and bears against the reenforcing ring 24 and serves to hold it in place.

,The contact lingers 29 by their engagement with the contact tip 21 in the groove 28, not only serve to provide a low-resistance, high-currentcarrying path between the tting 33 and the contact tip 21, but also serve to frictionally grip the latter and thereby tend to hold it and the tubular terminal 26 in place. For reasons which will appear hereinafter, it is desirable to hold the tubular terminal 26 stationary immediately after the current responsive element parts so that the operating mechanism will move the terminal 26 first to thereby take up the slack in a lost motion connection, which will be described presently, and effect the early release of an arcextinguishing iiuid into the bore 2U for scavenging its surface and assisting particularly in extinguishing low-current arcs. As is shown best in Figures 1A and 1B, an electrical connection between the line terminal Il and the contact ngers 29 is vprovided by a conducting tube, or terminal extension, 34 of brass, copper, copper alloy or other suitable conducting metals. It will be noted that the lower end of the conducting tube 34 is threaded onto the contact litting 33 and that a nut 35 is threaded onto the upper end of the tube 34 and also is threaded into the line terminal Il, thereby forming an extension thereof. A lock nut 36 serves to hold the contact nut in place.

As will hereinafter appear, it is desirable that when the fuse blows, the tubular terminal 26 be withdrawn through the bore 2D in order to extend the arc therein and permit the heat thereof to evolve an arc-extinguishing medium, such as water vapor, from the bore 205 so as to deionize the arc space and assist in extinguishing the arc. For extinguishing low-current arcs additional means are provided. In order to move the tubular4 terminal 26 a helical ,compression spring 31 lies within the conductor tube 34 and at one end bears against the fitting 33 and at the other end against the underside of a spring seat 38 which is secured to the lower end of a compression tube 39 that may be formed of brass. The compression tube 39 carries a base 40 at its upper end from which a stud 42 depends. On opposite sides of the lower end of the stud 42, straps 43 (only one of which is shown) are pivoted `by a pin 44. Between the straps 43 a pulley 45 is rotatably mounted on a.

pin or shaft 46.

A cable assembly, shown generally at 41, extends over the pulley 45 and provides both mechanical and electrical connection to the tubular terminal 26 for eiiecting retraction thereof and for maintaining electrical circuit connection thereto while it is being moved through the bore 26 after the contact tip 21 has moved away from the contact fingers 29. The cable assembly 41 consists of a core 48 formed of a large number of strands of line wire, such as copper wire, and an outer sheath 49 formed by a closely-wound coil spring, preferably of stainless steel. One end of the cable assembly 41 is connected by a strap or cable link 59 to the terminal fitting 33. It may 5 be secured thereto by suitable means, such as screws 5I, as illustrated more clearly in Figure 2 of the drawings.

The other end of the cable assembly 41 has a threaded terminal 52 which is screwed into a connecting tube terminal 52. The upper end of a connecting tube 53 is secured, as by rolling, to the terminal 52' and its lower end 54 is reduced and has a needle-holder pin 55 extending transversely therethrough. The pin 55 carries a generally cylindrically shaped needle-holder 56, the sides of which are slabbed off as indicated at 51 in Figures 2 and 3, to permit the free liow of arcextinguishing liuid therepast. The needle-holder 56 has an integrally formed tubular extension 58 which is deformed onto one end of a strain wire 59 which forms a part of the current responsive means employed in effecting operation of the fuse as will be described in detail hereinafter.

The needle-holder 56 carries a needle 63 which is notched as indicated at 64 to permit the escape of an arc-extinguishing uid as soon as a diaphragm 65 of a reservoir cr flask 66 is punctured. The reservoir or flask 66 may be a carbon dioxide capsule of a well known type. As soon as the diaphragm 65 is punctured the liuid in the reservoir 66 can escape in the form of a gas past the notch 64 of the needle 63 and the slabbed oif sides 51 of the needle-holder 56 into the tubular terminal 26 and out the lower end thereof.

The reservoir or liask 66 is secured in a tubular holder 61 which, as indicated, may be shaped to conform to the contour of the flask. The lower end 68 of the holder 61 is reduced in diameter and is threaded into the contact tip 21. It will thus be apparent that the reservoir 0r liask 66 is directly mechanically connected to the tubular terminal 26 and that it has conjoint movement therewith.

It is necessary to provide for relative movement between the needle-holder 56 and the reservoir or flask 66 in order to permit the needle 63 to rupture the diaphragm 65. For this reason a lost motion connection is provided between the connector tube 53 and the tubular terminal 26. In effect, a lost motion connection is provided between the tubular terminal 26 and the operating mechanism, which latter includes the coil compression spring 31, so that a limited movement of the operating mechanism is permitted be- ;'5 fore the terminal 26 is caused to move. This movement'isfsu-cient to causeV the needle '63 to rupture the diaphragm 65.

` AThe desired lost motion connectionis provided by a'slot'GS in the lower en d 680i the holder 61, through which'the pin 55 projects.

Initially, as illustrated in Figure 1B, the pin 55" is atthe lower ends of the slots 69.v When the strainv wire 59is no'longer restrained, as' when the 'current responsiveelement parts, the needleholder 56 is no longer restrained and it-begins to move upwardly under'theforce of the coilcompression spring 31.- Because'of the lost motion of the pin 55 in theslotted openings 69, the tubular terminal 26 is not moved immediately. Moreover, it is retained in the initial position by the fric: tional engagement of the contact fingers 29 in'the groove 28. Adeduate'lost motion is provided so that the impact oi the moving parts 53, 41, 39, etc., against` the stationary parts 26, 66, 61, etc., will drive the needle 63 throughl the diaphragm 65 and into the reservoir or flask 66 to the extent indicated in Figure 2. In this position the'pin 55 engages the upper ends of the slotted openings 69 and, thereafter, the "coil compression spring 31 isefective for withdrawing the tubular terminal 26 through the bore 2n. At the lower end of the tubular terminal 25 a tubular arcing tip 1I is carried. Fluted openings, Figure 7, y12 in the arcing tip 1l direct the fluid arc-extinguishing medium from the inside of the tubular terminal 26 along the surface of the bore 20 at the receding end of the tubular terminal 26, thereby directly sweeping over the surface of the boro 26 and removing therefrom particles of conducting matter or the like which may facilitate the restriking of the arc once it has been extinguished.

While the rcarbon dioxide blast is. especially helpful in the interruption of small currents it is also of material help in the case of high currents. In either case, it persists after the extinction of the arc and so sweeps out all residual ionized and conducting particles from the space between the arcing terminals andi increases the rate at which the arc-space builds up its resistance to any tendency of the arc to re-strike in response to the recoveryvoltage that appears at the fuse terminals promptly after the arc interruption. The tip 1|, by directing the carbon-dioxide blast over its outside surfaces, keeps the arc near the center of the tip so that metal at the arc root will not flow to the `side of the tip to there solidify and impede the free movement of the terminal through the close-fitting bore 2B.

As shown more clearly in Figure 1B, the strain wire 59 has a reduced section 13 adjacent the lower end ofthe arcing tip 1|. The purpose of this'is to provide a portion of thefstrain wire 59 which will melt in `preference to other parts of this wire on the occurrence of relatively heavy fault current. It will be apparent that when the section 13 melts, the resulting arc will be formed near the end ofthe tubular arcing tip 1l yso that' full use can be made of the bore 2l) for drawing the arc therein to aid in extinguishing it.

yThe lower end ofthe strain wire 59 is secured in a tubular terminal extension 14 of a terminal 15. The extension 14 is deformed ontothe end of Ithe strain wire 59` for providing mechanical and velectrical connections to it.

.As indicated hereinbefore, it may bedesirable to employ'the fuse construction of the. present invention forprotecting potential transformers. The normal current flow to the potential transformer is relativelysmall and, under .certain conditions, theflow of fault current thereto may also 8v be small butv yet Qfsueientl amount te require that the eireuit'bef interrupted; Thus; itis neeeSSarv te provide eurrent-resneasive' element which is Capable etreleasinathe Strain-Wire 59 ata relatively small overload' but which still .has suiiicient mechanicalvr strength to restrain Vthe movement of avpoweriul spring; such as the coil compressionL spring 31.` For this'purpose-a fuse link construction, indicateclgenerally at 16,may bev employed. The details of construction of the fuse link assembly 16 are setjforth in Lindell Patent` No. 2,804,495. Accordingly, onlyfsuch reference willihereb'ejmade aswill provide a brief Inutline'ofthe lconstruction of the'fuse link assembly 16.

The fuse link assembly. 16 vinelutlesj aterminal 11- which may be threaded intg'the terminal 15. One. end of a. eenfiiletins lilik. 18 is riveted tothe terminal 17 andtheether 'Lend has anf'eye that receives a lever 16^`which isthe first of. a set of interrelated levers comprising 4additional levers 8U and 8|. The levers 19, SU and 8i. are fulcrumed between plates 3-2 (enly one of .which is shown) of insulatingfmaterial that, in turn, are supported ona terminal 83'.. fusible element 84 in the form of a'relatively ne Wire mechanically and Aelectrically"connects the lever 8l with the terminal 83. "'Th'e size of .the wire 84 deter mines the timecurrent characteristics oi the fuse linkV assembly 16.` `Because cf the mechanical advantage provided bythe levers 19, Si) and 8l, the fullforce of thev spring 3.1 is not applied di.- rectly to the fuse'wire 84, Accordingly, it can be calibrated to melt on flow of a predetermined low current with: an accuracythat would be impossible if the wire 84 Weller'equired towithstand the full force of the spring 31. v

The fuse link assembly 1 6 is particularly intended to operatek when' the .iiow of fault current is relatively low and persists `over an extended period. In such case, the fuse wire B4 will nally part and release the levers 1,9, 8 0 and 3l, whereupon the spring 31A acts, as described hereinbe.- fore, to first puncture the diaphragm 65 and release the arc-extinguishing fluid from the reservoiror flask 56 into thc'tubular terminal 26. v In this case the arc will be drawn between the receding end of the'link 18 and the terminal y83. Terminal members and 11 .and link 1 8 are small enough to enter the bore 30 for ,extending the arc therein to be extinguished. The. arc will be of relativelysmall'current magnitude and the arc-,extinguishing fluid from. the reservoir or flask 65 Will materially .assist .in extinguishing .it since the'heat developed by thear is unlikely to be ,suicient to evolvethe necessary lamount ,of arc-.extinguishing medium from. the cakes vlil of arc-extinguishing material.

When. a relatively heavy fault lcurrent flows, yas

in the case ora .primary lshort circuit, both the,

redueed section 13er the Strain wire 5.9, and the fuse wire 84 willzmelt immediately. Thewiunetioning of the spring 3 1 ini withdrawing. the tubular terminal .2,5 and releasing .the arc-.extinguishing `fluid from the reservoir or `iiask 66 will be same ,as .already described. The terminal 11, bes ing thus left unsupponted, simply falls harmlessly into the exhaust passage.

The .terminal 8,3.is connected to the lower fuse tube terminal .l2 bya. rod 85. The lowerend of ther-.0d 85, asv viewed in Figure 1C,.is.seoured to a ,narrow bridge BB-.thatiscarried bya metal ex?. haust ltube .81. The Vmetall exhaust tube ,81 ex.-

tende` Well'up inte .the lower enelk 0i .the il-lSe tube.

I0 for assisting in more uniformly distributing the electrostatic stress incident to circuit interruption, as is set forth in more complete detail in the copending application of Lindell and Baker, Serial No. 663,832, referred to hereinbefore. A nut 88 is threaded onto the lower end of the tube 81 and is also threaded into the lower fuse tube terminal I2 to provide connection thereto. A lock nut 89 holds the nut 88 in place.

In order to hold the condenser shell |6, a reducer fitting 92 is threaded into the lower end of the lower line terminal I2 and the shell I6 is threaded thereon, as illustrated in Figure 1C. Within this condenser shell I6 is a condenser 93 of the type shown in Triplett Patent No. 2,379,200 which serves to cool and condense the products of the arc resulting from the blowing of the fuse as previously described.

It is desirable that the condenser shell I6 be closed to the atmosphere except when the fuse blows. For this purpose a valve seat 94 is threaded into the lower end of the condenser shell I6 and a valve cover 95 is arranged to cooperate therewith. The valve cover 95 is slidably mounted on the valve seat 94 by a stud 96 and is held in the closed position by a coil compression spring 91 which reacts between the upper surface of the valve 94 and a nut 98 at the upper end of the stud 96. When suicient pressure is generated within the condenser shell I6 on the blowing of the fuse, the arc products expand through apertures 99 in the Valve seat 94, lift the valve cover 95 from the valve seat 94 and exhaust into the atmosphere. Three pins (two of which are shown) extend upwardly from the valve seat 94 and serve to hold the condenser assembly 93 in place in the shell I6.

It will be recalled that the fuse construction disclosed herein can be employed as part of a dropout fuse construction as shown in the copending application of Lindell, S. N. 663,834. It is for this purpose that the latch tube I3 (Figure 1A) is provided. When the fuse blows and the compression tube 39 is driven upwardly by the spring 31, it carries with it the base 40 until the latter engages a cap |04 that is secured to the upper end of the latch tube I3. Thereupon, the latch tube I3 is moved upwardly, as illustrated in Figure 5A to lift therewith the flange i4 which releases the latch in the fuse mounting (not shown) so as to permit the fuse to drop out. The latch tube I3 moves upwardly until a flange |05, shown in Figure IB, on the spring seat 38 engages a shoulder |06, Figure lA, on the inside of a stop tube |01 that is secured to a fitting |08 which forms part of the fuse mounting contact mechanism, that is described in more detail in the copending application of Lindell, Serial No. 663,833. The stop tube |01 is held in place in the fitting |08, in part, by a sleeve |09 over which the lower end of the tube |01 is rolled and which bears against the underside of the fitting |08. The latch tube I3 is held in the position shown in Figure 1A of the drawings by a coil compression spring lll] which is located between the tubes I3 and |01 and at its lower end bears against the upper end of a tubular extension III from the flange I4 and at its upper end against the underside of a collar I l2 which is secured to the upper end of the stop tube |01. The fitting |08 has integrally formed ears I I3 and |I4 on opposite sides between which links are pivoted to provide for contact engagement between the line terminal I I and the cooperating fuse clip'.

At the end of the stroke of the operating mechanism, which includes the spring 31, theI connecting tube terminal 52 and connecting tube 53 occupy the position shown in Figure 5A and further upward movement thereof is prevented. During the movement of the tube 39, the accelerating force of the spring 31 opposed by the inertia of terminal 26, capsule 61 et cetera, tends to hold the needle 63 against the diaphragm 65 of the capsule 61. However, both the fluid pressure within the capsule 61 acting against the needle, and the kinetic reaction of the escaping jet of fluid tend to lift the capsule olf the needle.

In any event, at the end of the stroke, terminal 52 on the connecting tube 53 strikes pulley 45 and stops suddenly. The lost motion at the slots 69 then permits the momentum of the capsule 61 and of the terminal 26, which is connected to it, to carry the capsule up to the limit of motion permitted by slots 69 and so insure that the needle is disengaged from the opening for free egress of the last of the stored arc-extinguishing fluid.

As shown in Figure 6A, I take advantage of the strong forces that are available for lifting the capsule olf the needle. There a solid needle 63' is employed for rupturing the diaphragm 65 immediately after the current responsive wire melts. It will be apparent that the magnitude and effectiveness of those forces will depend in part on the size and shape of the needle itself. Thus, a needle having a large angle at its apex will have less tendency to wedge into the hole that it pierces in the diaphragm 65. The characteristics of the diaphragm material, such as its compliance and surface condition, will also affect the tendency of the needle to stick. I have found that a hard steel needle with a polished conical point having a full angle of 30 and driven into the thin steel diaphragm of the commercially available CO2 capsule, is ejected from the opening in the diaphragm early in the travel of the terminal rod 26.

Advantage is taken of the withdrawal of the needleat the end of the stroke by so constructing the solid needle 63 in Figure 6A that it lodges in the hole. Then, when it ruptures the diaphragm 65 immediately after the fuse blows, it, in effect, seals the opening thus made. While the seal thus formed is imperfect and some of the arcextinguishing fluid can escape from the reservoir or flask 66, it is not as free so to do as in the case of the other constructions. The needle 63 is freed from the diaphragm 65 by the sharp blow at the end of the stroke. Thus, the introduction of the arc-extinguishing fluid from the reservoir or flask 66 into the tubular terminal 26 is delayed until the operating mechanism has reached the end of its travel and the arc has been drawn out to its full length. At that time the arc-extinguishing fluid in the reservoir or flask 66 is free to escape past the needle-holder 56 into the tubular terminal 26.

As illustrated in Figure 6B, it may be desirable to omit the low-current fuse-link assembly 16, shown in Figure 1B and connect the strain wire 59, having the reduced section 13 therein to provide a preferred blowing section, directly to a connector I|8 that may be supported by a narrow bridge |I9 secured mechanically and e1ec trically to the exhaust tube 81.

Where a still higher current rating is required, a fusible element |20, in the form of a coil of silver wire can also be used. As illustrated in Figure 6B the coiled fusible element can be interconnected between the arcing terminal 1| and the connector l I8 by having the .ends thereof .deformed thereon. l

It will now be apparent that thestrain wire 59, in each of the embodiments of the invention disclosed herein, is directly tensionedby the operating mechanism which includes thecoil compression spring 3l andthat the stra-in wire 59 does not directly restrain movement of the tubular terminal 26. Rather, there is provision for relative movementbetween the operating mechanism andthe tubular terminal 26 so as to permit a slight movement of the former before the latter is moved for the purpose of releasing the arc-extinguishing. iiuid from the reservoir or flask .66 immediately. yupon the meltingof the current responsive element.

Since certain further changes can Ybe made in the foregoing constructions and dierent embodimentsof theinvention can be `madefwithout departing fromthe spirit and scope thereof, it is intended that all matter .shown` in the accompanying drawings and described hereinbefore shallbe interpreted as illustrativeA and not in a limiting sense.

What is. claimed as new is:

, 1.1. In circuit interrupting. apparatus, in combination, a body .of arc-extinguishing material having a bore, Va pair of relatively movable terminal membersl between which 4an arc maybe formed, one of said terminal. members Abeinglocated-adjacent one endy .of said bore andy the other -beinglrodlike in character I,and.movable througlrsaidbore, a'reservoir for holding material which when releasedis in the form-of an arc-extinguishing vuid,v -said reservoir being :located adjacent the end of said rodlike terminal membery away fromV the arcing-'end-lthereof, mechanism for fmovingisaidqrodlikei vterminal member, and a rupturing -memberresponsive to the initial movement of said lmechanism for puncturing said vreservcirand releasing said fluid into said bore and the arc space vfor assist-ing -in extinguishing `the arc before and while -said 'rodliketerminal member is withdrawninto said bore and'for blowing outfof-said-bore products` of the arc deposited'on the surface thereof and'likeljsr to facili-tate restrilring.-

2. In circuit interruptingapparatusin combination, a body of arc-extinguishing material havinga bore, a pair of relatively movable `terminalmembers between Awhich an arc may be formed, one of said'terminal members-being located adjacent one end of said bore and the other being rodlike in character A,and Amovable through said bore, a reservoir for-holding. material which when released 'is in-the-formofan arc-extinguishingf fluid, mechanismiifor `moving said rodlike.v terminal member, losmnoti'on means mountingl said reservoir adjacent-thegend ofgsaid rodlihe lterminal member away from-fthe r arcing endfthereof and serving-to hold the same stationary relative to said'mechanismf during-the initial movement thereof, f and meansl vresponsive to said' .-initial movementfof said mechanismf for releasingl said fluid Y into' saidff'bore and` the arc spacer-for assisting in extinguishing-the arc before yand while said rodli-keterminal member is withdrawn into-said bore andffor'blowing out of. saidbere...productsfof` Vthe'arcdeposited on the surface thereof and likely to facilitaterestriking,` said. :reservointhereafter beingmoved withA fsaid rodlike terminal member-to'the-end offthe stroke of saidmechanism. y i

3. In circuit .interruptingapparatua in combination, a. body of arc-extinguishing material having .-a..bore,. a pair.of relatively movable` terminal members between whichan -arc maybe formed-.oneof said-.terminal members lbeing 1ocated adjacent vone end ofsaid bore and the other being .tubular in vcharacter and `movable through said bore, asreservoir for holding material which when. released is in the form of. an arc-extinguishing nuid, saidreservoir being located adjacent the end of saidtubular terminal'member away from .the arcing end. thereof, mechanism 'for moving said tubular terminall member, anda rupturing memberresponsive to the initial-movement of said mechanism `for puncturing said reservoir and-'releasing said fluid to flow through said tubular. terminalmember into said bore. and the arc space during .the initialmovement of said mechanism for assisting in extinguishing the arc before .and while the same iswithdrawn` into said bore andfor blowing out of said bore products of the arcdeposited on the surface thereof and likelytofacilitate. restriking.

4. In circuit interrupting apparatus, in combinationha body of arc-extinguishing'material having a bore, a .pair of relativelymovable terminal members between' which an arc'mayfbe formed, one `of said terminal members being located adjacent one end of 4said bore and the other being .tubularin character and movable through said-bore, a reservoirfor holdingmaterial which when releasedis inthe form ofan arc-extinguishingfluid, mechanism for moving said ytubular terminal member, lost mot-ion lmeans mounting saidwreservoir adjacent the end of said tubular terminal .member -away from rthe arcing -end thereof .and serving to hold :the same stationary relative to said mechanism during the initial movement thereof, andmeans responsive to said initialA movement of said mechanism for releasing said uidvto flow through saidtubular terminalfmember into said bore andthe-.arc space for assisting in. extinguishing the arc before and while said tubular terminal .member is withdrawn into said bore andfor Vblowing out of said bore products of the arc deposited on the surface thereof fand` likely to facilitate restriking, said reservoir thereafter being moved .with said tubular -terminalmember to Vtheend of the stroke oi.' said mechanism.

5. In circuit interruptingapparatus, in combination,; a bodyof arc-extinguishing material having a, bore, a pair of relatively movable terminal members between which an arc maybe formed, one of said terminal'members being positioned adjacent vone end of said boreand'the other being rodlike. in character and movable through said bore-,a -capsulemounted for movement Awith said rodlike terminal member and .containing material which when released is in the form of an arcextinguishing -fluid, a diaphragm ksealing `said capsule, mechanism vfor moving saidv rod-like terminal fmemberand having a lostmotion connection Atherewitl'-l,.and Ymeans moved by said mechanism -While it takes up the r`slaclrin said lost-emotion connection for puncturing said diaphragm to release said iluid into said bore and arc -space for -assisting'in extinguishing the arc before and while -said-.rodlike terminal member is withdrawn into saidbore.

6. In a circuit interrupting apparatus, in combination,v a body of arc-extinguishing material having an arc-passageway therein, means for drawing an arc =in said passageway including a` stationary .terminali-and a terminal movable throughsaid-passageway, a* reservoir mounted for imovement' with said 'movable terminal 4and containing material which when released is in the form of an arc-extinguishing fluid, spring biased mechanism for moving said movable terminal, lost motion means interconnecting said movable terminal and said mechanism and ar ranged to permit movement of the latter relative to the former to take up the slack therein, means operated by said mechanism while taking up said slack to release said fluid into said passageway, and fusible means interconnecting said stationary terminal and said mechanism for restraining movement of the latter until the fusible means blows.

7. The invention, as set forth in claim 6, wherein the movable terminal is tubular and the arcextinguishing fluid flows therethrough into the arc-passageway.

8. The invention, as set forth in claim 6, wherein the movable terminal is tubular and the arcextinguishing fluid flows therethrough into the arc-passageway and the fusible means is a part of a high tensile strength conductor which eX- tends through the tubular movable terminal.

9. The invention, as set forth in claim 6, wherein the fusible means comprises a fusible element interconnecting the stationary and movable terminals and a strain wire interconnecting said stationary terminal and the spring biased mechanism.

10. The invention, as set forth in claim 6, wherein the movable terminal is tubular and the arc-extinguishing fluid flows therethrough into the arc-passageway and the fusible means comprises a fusible element interconnecting the sta tionary and movable terminals and a strain wire extending through the tubular terminal and interconnecting said stationary terminal and the spring biased mechanism.

1l. The invention, as set forth in claim 6, wherein the movable terminal is tubular and the arc-extinguishing fluid flows therethrough into the arc-passageway and the arcing end of said tubular terminal has at least one aperture placing the opening therein in communication with the arc-passageway to direct the flow of the arc-extinguishing fluid onto the surface thereof.

12. In circuit interrupting apparatus, in combination, a body of arc-extinguishing material having an arc-passageway therein, means for drawing an arc in said passageway including a stationary terminal and a tubular terminal movable through said passageway, a reservoir, a rupturable diaphragm sealing said reservoir, said reservoir containing material which when released is in the form of an arc-extinguishing fluid and being mounted for conjoint movement with said tubular terminal at the end remote from its arcing end, spring biased mechanism for moving said tubular terminal, lost motion connecting means interconnecting said tubular terminal and said mechanism whereby movement of the latter relative to the former is permitted to take up the slack therein, a needle movable with said mechanism while said slack is being taken up and before said reservoir is moved for puncturing said diaphragm torelease said arc-extinguishing fluid to flow through said tubular terminal, and fusible means interconnecting said terminals including a strain wire extending through said tubular terminal and connected to restrain said mechanism until the fusible section blows.

13. The invention, as set forth in claim 12, wherein the needle has a relieved section vintermediate its ends which registers with the ruptured diaphragm to facilitate the escape of the arc-extinguishing fluid immediately upon puncturing thereof.

14. The invention, as set forth in claim 12, wherein the needle has a uniform cross section.

15. In circuit interrupting apparatus, in combination, an arc confining structure having a bore, a pair of terminal members between which an arc may be formed, one of said terminal memlike terminal member away from the first terminal, lost motion means mounting said reservoir adjacent the end of said rodlike terminal member away from the arcing end thereof and serving l to hold said rodlike terminal member stationary both before and during the movement of said during the initial movement of said mechanism, and means responsive to said initial movement for releasing said fluid into said bore and into the arc space for assisting in extinguishing the arc rodlike terminal member into said bore and for blowing out of said bore products of the arc deposited on the surface thereof and likely to facilitate restriking, said reservoir being moved with said rodlike terminal member to the end of the stroke of the said mechanism.

16. In circuit interrupting apparatus, in combination, a pair of terminal members between which an arc may be formed, one of which is tubular, Ia reservoir for holding material which when released is in the form of an arc-extinguishing fluid, mechanism for moving said tubular terminal member away from the other terminal to enlarge the arc distance between them, lost motion means mounting said reservoir adjacent the end of said tubular terminal member away from the arcing end thereof and serving to hold said tubular terminal member stationary during the initial movement of said mechanism, and means responsive to said initial movement for releasing said fluid into the arc lSpace between Isaid terminals for assisting in extinguishing the arc before and while said tubular terminal member is being Withdrawn and for blowing out of said space products of the arc likely to facilitate restriking, said reservoir being moved with said tubular terminal member to the end of the stroke of the said mechanism.

17. In a circuit interrupting apparatus, in combination, means defining an arc space and for drawing an arc therein including a pair of arcing terminals one of which is tubular, a reservoir, a rupturable diaphragm sealing said reservoir, said reservoir containing material which when released is in the form of an arc-extinguishing fluid, said reservoir being mounted for conjoint movement with said tubular terminal at the end thereof remote from its arcing end, spring biased mechanism for moving said tubular terminal relf ative to the other terminal, lost motion connecting means interconnecting said tubular terminal and said mechanism for providing a driving connection with limited relative movement therebetween, fusible means for initiating an arc between said terminals including a. strain wire extending through said tubular terminal and connected to restrain said mechanism in such position that upon rupture of said strain wire said mechanism must take up the slack of the relative movement between said mechanism and said tufbular terminal before driving said terminal, and

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a `needle,movable:vvitli said mechanism Awhileisaid slaclnisbeing takenun and .before said reservoir and tubular terminal are moved, for .puncturing said diaphragmtoirelease the arc-.extinguishing fluid to ,flow Athroughsaid .tubular terminal.

18. In combination `in a. circuit Ainterrupter having ra-ibodybf arceXti-nguishing material inv which thereiis-alongitudinally ,extending bore, a tubular .arcing terminal, ,a reservoir of arc-extinguishing `material atvone end of said` terminal adapted to, dischargek said, material through said tubular. ,terminal for ,assisting in extinguishing an arc drawn, thereat, .driving .means Y for moving said terminal.longitudinally through said. bore in the direction oi said .one end while said arc extinguishing material .is being discharged throughaid, tubularA terminal, `a, tension element extending through said tubular Yterminal for restraining said drivingrmeans,l said. terminal having .a longitudinal slot, a pin extending through said slot yfor connecting said tension element tolsaid driving meanssaidslot,permitting limited .relative movement between said terminal anddriving means, and acover for said slot.

19. In circuit interrupting apparatus, in combination, a body 0f arc-extinguishing material having a bore, a pair of relatively movable .terminal members between ,which an arcmay be formedone of said terminal members being ,located'adjaicent one endiof said bore and the other beingjrodlike in character, and movable through, said bore, means. for retracting said rod1ike' -termina1member away from said one terminal member, Contact means frictionally en gaging said rodlike terminalmembel` and providing a, current path thereto prior to movement thereof by said retracting means, and means for controlling the movement of` said rodlike ,terminal member away from said one terminal membefin'cluding a lost motion connection between said retracting means. andV said rodlike terminal member whereby on operation of said controlling means said-retracting means moves through a predetermineddistance without moving said rodlikej'terminal member andacquires kinetic energy to assist in overcoming the friction between said rodlike terminal member and said contact means in initiating the movement vof the Vfermer away from'said one terminal member.

20. In circuit interrupting apparatus, in combinationsa body'of arc-extinguishing material havinga bore, avpair of relatively movable terminal membersfbetween which an arc may be formed, one of said terminal members being located 'fadiacentoneend of said bore and the other ibeing'rodlike' 'in character and movable through-said bore, means for retracting said rodlike` terminal member away from said one terminalmember, :contact means -frictionally engaging-said Yredlketerminal -member and proavidingv 4a current'fpath thereto yprior to movementthereof bysaid retracting means, and means for controlling the movementl of said rodlike terminal-member away fromsaid one terminal member including a lost motion connection betweensaid retracting means andy said rodlike terminalmember and a fusible elementvwhereby on blowing-of saidfusible element said retracting means-moves through a, `predetermined distance withoutI movingsaid lrodlikeV terminal member and acquires kinetic energy to assist in overcoming-=the friction --betweensaid -rodliketerminal member vand said` contact means in initiatingthe `movement of the former away from said one terminal Y menlberj 2l. In cincuit interrupting apparatus, vincomf bination, a body fof arc-,extinguishing 'material having a bore, a, pair, of relatively movable terminal members between which an arc `may be formed, oneof said terminal members being'lof cated adjacent oneend of said bore and the other being rodlike in character and movable through said bore, a reservoir for holding` material which when released is in the form of an arcfextinguishing-fluid, saidreservoir being ,located adjacent the end of said rodlike terminal member away from the arcing vend. thereof, means for retracting said rodlike terminal member away from said one terminahmember, contact means` frictionally engaging said rodlike terminal member and providing a currentpath thereto prior, to movement thereof by said retractingmeans, .means responsive to the initial vmovement of said retracting means. forreleasing. said fluid .into said bore and the arc space for assisting in extinguishing the arc before and .While said `rodlike terminal memberis Withdrawn -into said-bore andifor blowing outof said borev productsof the arc deposited von the-surface thereof .and-= likely to facilitaterestriking, and means for .controlling .the movement of .said rodlike terminal member awayv from .said one terminarmember including a lostmotion connection between said retracting means and said rodlike terminal member whereby von operation :of saidfcontrolling means said retracting means.- moves through -a predetermined distance without'moving said rodliketerminal memben releases said fluid and acquires kinetic energy toy assist in'iovercoming the friction between said rodlike'terminal member and said:contact means in. initiating the movement of the formerawayqfrom said -one terminal member.

22. vIn circuit interruptingy apparatus, in combination, a body; of arc-extinguishing material having a bore, a pair of relatively movableterrni nal members between which an arc may be formed-one of said terminal members being 1ocated adjacent one end of said bore and the other'being rodlike in character, and movable through said bore, a reservoir for holding material which when released is in the form of an arc-extinguishing fluid, said reservoir being located adjacent the end of said rodlike terminal n member away from the aroing endthereof, means for retracting said rodliketerminal member away from said one terminal member, contact means frictionally engaging said rodlike terminal member and: providingfa eurent path thereto prior to movement thereof by said retracting means, means responsive to the initial-movement of said,

retracting means for releasing said fluid into said bore and the arc space Afor assisting in extinguishingthe are beforeand while said` rodlike terminal member is withdrawninto vsaid bore and for vfblovvingvout of said bore products of the arc deposited on the surface thereof and -likely to facilitate restriking, andmeans for controlling the movement offsaid rodlike terminal member away from said one terminal member including a lost motion connection -between said retracting means'and said rodlike terminal member and -a fusible element whereby on blowing of said fusible element said retracting means moves through -a predetermined distance Vwithout mov-y ing said rodlike terminalimember, releasesl said fluid and-acquires kineticenergy to assist in overcoming vthe-friction between said yrodlike terminalmember andfsaid contact means-.in initiat 17 ing the movement of the former away from said one terminal member.

23. In circuit interrupting apparatus, in combination, a body of arc-extinguishing material having a bore, a pair of relatively movable terminal members between which an arc may be formed, one of said terminal members being located adjacent one end of said bore and the other being tubular in character and movable through said bore, a reservoir for holding material which when released is in the form of an arc-extinguishing fluid, said reservoir being located adjacent the end of said tubular terminal member away from the arcing end thereof, means for retracting said tubular terminal member, contact means frictionally engaging said tubular terminal memiber and providing a current path thereto prior to movement thereof by said retracting means, means responsive to the initial movement of said retracting means for releasing said fluid to ow through said tubular terminal member into said bore and the arc space during the initial movement of said reti-acting means, and means for controlling the movement of said tubular terminal member away from said one terminal including a lost motion connection be- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,319,276 Triplett May 18, 1943 2,343,422 Rawlins Mar. '7, 1944 2,353,523 Triplett July 11, 1944 2,435,533 Earle Feb. 3, 1948 

